The invention relates, generally, to telecommunications networks and, more particularly, to an improved interface card for use in such networks.
It will be appreciated that a typical telecommunications network consists of a plurality of switching systems, such as the 5ESS.RTM. switching system manufactured and sold by Lucent Technologies, connected together via trunks for the transmission of signals therebetween. Selected ones of the switching systems, commonly referred to as central office switches, are connected to customer premise equipment (CPE) such as telephones, multimedia equipment, fax machines or the like via customer lines. The customer lines can consist of any media suitable for transmitting voice and data including twisted wire pairs, coaxial cable, fiber optic cable or the like.
It is also known in the art to use remote terminals such as digital loop carriers, an example being the SLC.RTM. digital loop carrier manufactured and sold by Lucent Technologies Inc., between the central office and the customer premise. Distribution lines connect the central office switch to the remote terminal and customer lines connect the remote terminal to the CPE. In addition to the switching systems and digital loop carriers, other network elements such as broadband distribution elements, PBXs (public branch exchanges) or the like also host customer lines and/or trunks.
The switching systems, remote terminals and other similar network elements terminate the lines and trunks at line units and trunk units, respectively, commonly referred to collectively as interface units. Each line unit or trunk unit includes a plurality of line cards or trunk cards (also referred to in the art as application packs) removably inserted into a subrack or frame. For purposes of this application the line cards and trunk cards are referred to collectively as interface cards. Each line card typically hosts between 1 and 32 lines and each trunk card hosts between 1 or 2 trunks. It will be appreciated that the line cards and trunk cards include common circuitry for controlling functions common to all of the lines or trunks hosted by that unit as well as circuitry specifically dedicated to each line and/or trunk. The line cards typically include circuitry for performing the BORSCHT functions of battery feed, overvoltage protection, supervision, coding and decoding, testing as well as ringing. It will be appreciated that the specific functions performed by the line card circuitry can vary. For example, it is known in the art to provide the ringing function for all lines on a separate line card. It will be understood that the circuitry is service specific and that different line cards are used to provide narrowband, ISDN, COIN, special service or the like. The trunk cards include circuitry for performing coding and decoding, dc signaling, test functions, alarming and multiplexing. Thus, the line cards and trunk cards provide the basic processing for each line and trunk in the network and are the physical interface between the switching systems (or other network element) and virtually every line and trunk in the network. As a result, the cost, performance and ease of maintenance and administration of the interface cards are critical. Moreover, because a typical network includes thousands of interface cards, any improvement in the interface card translates to large benefits for the network operator and customer.
Each line card physically consists of a circuit pack containing the line unit circuitry and a face plate connected to one edge of the circuit pack. The line card is removably inserted into a subrack or shelf of the switching system (or other network element) such that the face plate is exposed to the system operator. The circuit pack includes first and second sets of connectors located on the side of the circuit pack opposite to the face plate. When the line card is inserted into the frame, the first and second set of connectors engage mating connectors located at the back of the frame. One set of connectors connect the line card to the backplane of the network element and the other set of connectors connect the line card to cabling that connects to the lines. Because these connectors are located behind the line units at the back of the frame, all of the cabling must terminate at the back of the frame. Because of the amount of cabling used in a typical network element and the location of the cabling in the back of the line unit, it is very difficult to increase the density of the system because additional cabling cannot be added in the limited space at the back of the line unit. The location of the cabling also prevents the line units from being arranged back to back. Moreover, because the cabling must be accessible, the back of the line unit must remain unobstructed. The location of the cabling at the rear of the line unit also requires that the entire line card be removed to disconnect the cabling from the line card. Thus, the location of the cabling makes the administration, maintenance and provisioning of the network element difficult and reduces the line density. These problems are magnified when it is considered that a typical switching system hosts thousands of lines connected to hundreds of line cards. While the above discussion relates specifically to line cards it will be appreciated that the arrangement of trunk cards is substantially the same.
It is also known in the art to make the cable connections using a plurality of pin connectors at the face plate of the line card, rather than at the back of the line unit. While using a plurality of connectors at the front of the line card facilitates access to the cabling, the line cards that use the front connectors rely on a plurality of separate connectors. The use of multiple connectors is relatively expensive and requires the connection and disconnection of a plurality of connectors to install a single line card. Not only is such a design expensive, it increases the time required to replace the interface unit and increases the risk of a misconnected cable.
Thus an improved interface card configuration utilizing a single, front mounted cable connection that is easily disconnected is desired.